50 Graminaceae 
AVENEAE. (Oats TRIBE)—Spikelets usually 2 to several flowered (so in 
ours), in either open or spike-like panicles. Rachilla usually produced beyond the upper 
lemma (except in Aira in ours), usually with tufs of hairs at the joints. Flowers perfect, 
or | of them staminate or abortive. Glumes 2, often persistent, usually longer than the 
first lemma. Lemma with tuft of hair at base; 1 or more lemmas in each spikelet awned 
(except in Trisetum muticum in ours); awn either dorsal or near the apex between the 
lobes, often more or less twisted and bent. Palet 2-keeled. Stigmas plumose. Grain fur- 
rowed or unfurrowed, free or adherent. 
A. Plants 2 dm. high or less; spikelets 2-flowered, both perfcats rachilla jointed below 
the glumes, not prolonged beyond the upper flower . AIRA (p. 50) 
AA. Plants mostly taller; spikelets 2 to several flowered, sometimes only | perfect 
when only 2; rachilla jointed above the glumes (except in Holcus), prolonged beyond 
the upper flower. 
B. Plants densely soft-whitish-hairy; spikelets falling off entire; rachilla jointed be- 
low the glumes; spikelets 2-flowered, the lower perfect, the upper staminate; awn 
of second flower hook-like. Hotcus (p. 50) 
BB. Plants not densely pa mA ELR Tig spikelets falling off in parts; rachilla 
jointed above the glumes; spikelets 2 to several flowered (2 only in Arrhenatherum, 
which has the perfect flower above) ; awns not hook-like. 
C. Spikelets 1 cm. long or less. 
D. Spikelets 8—10 mm. long; lemma awned from near. the base; spikelets 
only 2-flowered; upper flower perfect or pistillate, the lower staminate. 
ARRHENATHERUM (p. 51) 
DD. Spikelets either less than 7 mm. long or else lemma awned from the mid- 
dle or above it; spikelets 2 to many flowered; upper flower sometimes stam- 
inate or abortive, the others perfect. 
E. Lemma keeled, obtuse or truncate, erose at tip, awn arising at or below 
the middle. DESCHAMPSIA (p. 51) 
EE. Lemma convex, acute or shortly bifid, not erose, awn none or arising 
above the middle. TRISETUM (p. 51) 
CC. Spikelets over | cm. long. 
F. Perennial; awn of lemma between the teeth at apex; grain glabrous. 
DANTHONIA (p. 52) 
FR Annualcor perennial; awn of lemma dorsal; grain hairy. AVENA (p. 53) 
HOLCUS 
Agnual or perennial (ours), soft. Leaf-blades flat, or rarely folded. Spikelets 
2-flowered, deciduous as a whole, numerous and crowded in an open terminal panicle; 
lower flower perfect, on a curved stipe; upper one staminate or rarely perfect; rachilla 
jointed above the glumes. Glumes subequal, compressed, boat-shaped, acute or awned, 
projecting beyond the flowers, 3-veined, the second the wider. Lemma shorter than 
the glumes, boat-shaped, membranous, the lower awnless, the upper with a short bent 
dorsal awn. Stamens 3. Grain oblong, free. (Gk. holkos—some kind of grass.) 
W. E. H. lanatus L. (Velvet Grass) 
AIRA HAIR-GRASS 
Slender, delicate, annual. Leaf-blades narrow. Spikelets 2-flowered, small, in a 
terminal panicle; panicle loose or rarely contracted (in A. praecox), with capillary 
rays; rachilla jointed, minutely hairy, not at all or scarcely extending beyond the perfect 
flowers. Glumes thinly scarious, subequal, acute, exceeding the flowers. Lemmas close 
“ 
“5 pees coeds en 
seal inet atime 
a oe PO rs Peet. Yee) 
eS oe 
